   (when (.isUnimodularIntegerMatrix M)
     (let [sigs (node-signatures net)
           d (.minus (first (first (sigs w))) (first (first (sigs v))))
-          op (.times (Operator. (extend-matrix M)) (Operator. d))
-          check-sigs (fn [a b] (equal-sigs? (map-sig op (sigs v)) (sigs w)))]
+          op (.times (Operator. (extend-matrix M)) (Operator. d))]
       (loop [src2img {}
              q (conj empty-queue [v w])]
         (let [[a b] (first q)]

                     (into (pop q)
                           (for [d (keys nv)
                                 :let [e1 (.get nv d)
                                       e2 (.get nw (.times d op))]
                                 :when e2]
                             [e1 e2]))))))))))

(defn symmetries [net]

            (instance? IEdge a)
            (recur (assoc src2img a b) (conj (pop q) [(.target a) (.target b)]))
            
            (not (equal-sigs? (map-sig op (sigs a)) (sigs b)))
            nil
            
            :else
